1. Field of the Invention
The present invention relates to an amorphous iron based alloy having excellent magnetic characteristics as well as resistance to brittleness. The invention further relates to a method of manufacturing the amorphous iron based alloy.
2. Description of the Related Art
As disclosed in Japanese Patent Unexamined Publications No. 54-148122 (1979), No. 55-9460 (1980) and No.57-137451 (1982), when a molten alloy composed of Fe--B--Si or the like is ejected onto the surface of a cooling roll rotating at high speed, using the single roll method or the like, and is quenched and solidified at a cooling speed of about 10.sup.5 -10.sup.6 .degree. C./sec., a so-called amorphous alloy sheet can be produced with a thickness of about several dozens of microns and wherein the atoms are disposed in a disorderly arrangement.
Such an amorphous alloy sheet has low iron loss and high magnetic flux density and has excellent so-called soft magnetic characteristics when attempted to be put into practical use as a core material of a transformer.
Nevertheless, such a sheet composed of the Fe--B--Si ternary amorphous alloy has disadvantages. Although the sheet can achieve an iron loss value which is low to some degree, the improvement of iron loss is limited. A further reduced iron loss cannot be expected from a ternary alloy. To cope with this problem, attempts have been made to add various elements to the ternary amorphous alloy as a fourth component.
For example, Japanese Patent Examined Publication No. 1-54422 (1989) proposed an amorphous iron based alloy obtained by the addition of Mn, Ni and the like to an Fe--B--Si alloy in an amount of 0.5-3 at % (atomic percent) and the thus obtained amorphous iron based alloy had a low iron loss and excellent insulating film processing properties. However, when Mn is added in an amount of 0.5 at % or more, the material becomes brittle. Further, reduction of magnetic flux density becomes a problem in practical use.
Japanese Patent Unexamined Publication No. 62-192560 (1987) proposed an amorphous alloy obtained by adding one element or two or more selected from Cr, Mo, Ta, Mn, Ni, Co, V, Nb and W to a Fe-B-Si alloy, in an amount of 0.05-5 at %, and further subjecting the resulting alloy to a process such as rolling or the like for adjustment of surface roughness of the alloy.
However, Japanese Patent Unexamined Publication No. 62-192560 (1987) does not take brittleness into consideration. Further, even if the surface roughness of the alloy made into a sheet is adjusted by rolling or the like, such a process is doubtfully effective for reduction of brittleness. In addition, adjustment of surface roughness is industrially very ineffective and also disadvantageous as to manufacturing cost.
The present invention is directed to overcoming the aforesaid problems advantageously, and relates to an amorphous iron based alloy having excellent magnetic characteristics as well as resistance to brittleness. It is further directed to a method of manufacturing such a superior amorphous iron based alloy.